A case packer is designed to pack containers (typically bottles or cans) into cases or trays at speeds up to 40 cases per minute (cpm), depending on product specifications.
The typical case packer can be broken down into five major sections, the product infeed, case feed, lift table, grid and operator interface sections.
The product infeed section carries product toward the machine and separates it into the desired pack pattern using stainless steel lane guides. Product is typically monitored for volume and position throughout this section by a series of electronic sensors.
The case feed section transports empty cases into the lift table on a conveyor and discharges cases out of the machine after product has filled the cases. Cases are indexed into the lift table section using a series of stops, which prohibit cases from advancing in the case feed when activated. Case volume and positioning is monitored throughout this section by a series of electronic sensors.
The lift table section of prior art case packers lifts the cases to a point beneath the grid area and waits for product to enter the case before descending. This section is equipped with an air over oil lift table which prompts the up and down motion of the table. As the grid area is filled with product, the lift table rises. Once the product has successfully entered the case, the lift table lowers. The case feed then discharges the filled cases.
The grid section is responsible for releasing product into the empty cases on the lift table. This section is made up of two primary components: the riding strip on which the product rests as it enters the grid area; and the grid basket through which product descends once the riding strips are shifted. The grid components are typically changed to accommodate a new product size, depending on product specifications.
The operator interface section controls a system to manage the operation of the machine. In certain case packers of the prior art the interface is mounted on a swing boom which enables the operator to control the machine from either side.
Containers are fed into the product infeed from a product conveyor system. As the containers advance downstream, they are arranged into a nested pattern using a series of guides. The containers are monitored throughout the infeed using sensors such as a high-level detector, low level detector, void detectors and a down product detector.
The low level detector monitors the volume of containers entering the machine. If a shortage of product flow occurs, the machine will automatically come to a controlled end of-cycle stop and wait for additional product. The machine will then automatically restart when additional product is supplied. The void detectors monitor the volume of product entering the machine. In the event that the low-level detector is blocked indicating sufficient containers and a void detector senses no containers, the void detector will signal an infeed oscillator cylinder to actuate lane guides to move back and forth, freeing any potential container jams. If a jam is present, the freed containers will then flow downstream, block the void detectors and stop the infeed oscillator from actuating. The down product detector prevents fallen containers from entering the grid area. In the event of a fallen container, a detector signals the machine to come to a stop. The case feeds section is responsible for transporting empty cases into the machine. Empty cases enter the case feed from a conveyor and the first case comes to rest against a stop. The second case then comes to rest against the first case and relieves a low level condition signal allowing the two empty cases to enter the lift table section and come to rest against a lift table case stop. A pair of case brakes grasp the side of a subsequent case whenever a case in front of it is fed into a lift table. This prevents additional cases from flowing onto the lift table and interfering with normal operation. One problem with the case brakes of the prior art is the time consumption and difficulty associated with accommodating cases of different sizes.
The cases then exit the case feed section and enter the lift table. Once the first and second cases are positioned on lift table the lift table is raised upward toward the grid. At the same time a case clamp is closed, prohibiting the cases positioned on the lift table from moving backwards. As the cases exit the case feed the forward flap of the cases must be opened prior to presentation to the lift table. Typically an air cylinder having a helix drive and a shoe mounted to the end is employed. The air cylinder propels the shoe towards the leading flap end of the forward moving case and simultaneously rotates the shoe to lift and open the leading flap. Some of the problems with this type of flap opener include the relatively high expense of the helix air cylinder, high part wear and the timing and adjustment problems associated with case size changes.
Once the lift table advances upward two additional empty cases are allowed to advance downstream against the infeed case stop. Once the lift bale returns to its down position, both filled cases will be discharged at the same time that two empty cases will be entering the lift table. Once the first case is cleared, the lift table case stop will close and empty cases will then enter the lift table. The operation cycle will then repeat, based on the amount of containers in the product infeed. If there is a low product condition, the case feed will wait until all conditions in the product infeed and grid are satisfied before continuing.
The lift table section is responsible for positioning empty cases at a point beneath a grid basket. This section of the machine typically consists of an air over oil lift cylinder, which is controlled through the operation of several photoeyes and timers controlled, for example, by a programmable logic controller (PLC). The grid is activated to shift and to release the containers as will be more fully discussed herein below and filled cases are discharged from the machine on a conveyor. The grid section is responsible for arranging containers in their final pack pattern and ensuring that the containers lower into the case smoothly and in order. The grid consists of two primary components, the riding strips and the grid basket. The product infeed advances containers downstream onto the riding strips within the grid section. Overhead brakes lower into contact with incoming containers thereby prohibiting additional containers from entering the section. Once the overhead brakes are lowered, the riding strips are shifted to one side approximately xc2xd the diameter of the product. This allows the containers positioned in the grid to lower through the riding strips and grid basket into the empty cases positioned on the lift table.
Once the containers pass through the grid into the cases the riding strips are returned to their original position and the overhead brakes are raised and subsequent containers are moved from the product infeed into the grid. The process will then repeat itself, depending on the amount of containers entering the grid.
The lift table of the prior art as described herein has deficiencies associated with the high levels of shock loading transmitted to containers delivered from the grid and also from the stand point of machine speed. The containers, as they are dropped into the cases, experience shock loads on the average of about 15 to 25 times the force of gravity. Typical containers are comprised of glass and thin walled plastic which may shatter or rupture due to these types of shock loadings. The shock loading not only dictates container design but also a robust drive system for the table which increases the weight and momentum of the system, all causing wear and timing problems. The lift table experiences approximately 1500 pounds of shock loading, as the containers impact the cases, each cycle at a rate of up to 40 cases per minute.
Control of the case packer machine is managed through the operator interface, which is sometimes mounted on a swing boom on the side of the machine. This interface consists of a series of pushbuttons which enable the operator to start, stop, alter the performance of machine, and locate/correct any fault conditions.
The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the present invention.
This invention relates generally to machines for packing containers into cases. In particular this invention relates specifically to improvements to a case packer of the type where containers are dropped through grid fingers to an empty case positioned on a lift table. The improvements include a device for opening flaps on the case and a lift table section including an improved lift table drive assembly.
The case packer machine of the present invention includes a flap opener which includes a pair of shoes mounted to an air cylinder. The shoes are extended by the air cylinder to overtake the cases as they are advanced through the case packer machine to contact and open the leading flap. The shoes are biased in a retracted position by a tension spring and as the shoes contact the leading flap they work to rotate the leading flap toward an open position. As the shoes contact the leading flap they pivot about a pivot pin in a rod end of the air cylinder and disposed within a slot on the shoes. The shoes continue to extend to the point where they contact the leading comer of the case wherein the shoes rotate along a path defined by a cam slot and move the leading flap to an open position. When the cylinder is retracted the shoes are retracted by the biasing force provided by the spring.
The lifting table of the present invention is motor driven and controlled to limit the shock loading experienced by the containers as they are positioned within the cases. The lifting table includes a pair spur gears driven by the motor in meshing arrangement with a pair rack gears each mounted to a table and a novel gear guide to maintain proper engagement between the racks and gears and further to provide for backlash adjustment between the gears. A vibration and shock absorbing mount is used to position the motor to the machine to eliminate shock loading effects on the drive system and on the containers themselves.